The liquid nutritional industry is a multi-billion dollar a year business. Infant formulas and medical nutritionals comprise the major portion of this industry. "Nutritionally complete" formulas such as infant formulas and medical nutritionals, are required to contain significant levels of minerals, vitamins, protein, carbohydrates and fat to provide the required level of these nutrients to a human in an acceptable volume. These nutritionally complete formulas allow for the formula to be the sole source of nutrition for a human consuming same. The presence of certain minerals, such as calcium and phosphorus, is vitally important to the efficacy of the nutritional. However, the presence of these high levels of minerals, protein and fat cause a number of significant problems in the manufacture and use of these formulas.
Nutritionally complete liquid formulas have traditionally been plagued with the problems of creaming and sedimentation. Creaming occurs when fat globules in the liquid nutritional float to the top of the product. These fat globules can harden and block or clog feeding tubes or nipples. In sedimentation, various insoluble components of the liquid nutritional settle to the bottom of the product container. Of particular concern is the sedimentation of calcium, phosphorous, fibers and flavoring powders, such as cocoa. Cocoa powder is especially prone to sedimentation and when cocoa powder sediments, it is not easily redispersed. The sedimentation of these elements is further aggravated when the sediment hardens into a cementous type of material known as "non-dispersible sediment". The problem with non-dispersible sediment is three fold: (1) the liquid nutritional is now subject to nutrient deficiency, since the non-dispersible sediment often refuses to go back into solution upon the shaking of the container; (2) the sediment will plug feeding tubes or nipples; and (3) the product appearance is negatively affected, for example, the product appears "spoiled" to the consumer.
The liquid nutritional industry, in the past, has focused on reducing sedimentation through the use of stabilizers such as carrageenans and celluloses. While the formation of non-dispersible sediment is delayed through the use of the prior art stabilizer systems, it has not been prevented. One feature of the present invention resides in the discovery that gellan gum, while not preventing sedimentation, allows for the redispersion of the sediment upon shaking without creating a significant amount of non-dispersible sediment.
Numerous stabilizing systems have been proposed to address the sediment and creaming problems in a nutritionally complete formula These solutions however, resulted in limited success. Stabilizing systems known to date allow the minerals, fibers and flavoring powders to be suspended longer, however, they ultimately fall from solution. Typically, stabilizing systems or suspenders of insolubles are locust bean gum, guar gum, carboxymethylcellulose, lambda carrageenan, konjac flour and the like. These stabilizers are known as "non-gelling" or "weakly gelling" types. These stabilizers require fairly high addition rates (1200 ppm and higher) and high resulting viscosities (above 50+ cps or 0.05 Pa.cndot.s) to achieve acceptable levels of suspension.
The problems associated with physical stability of nutritionally complete liquid formulas have been addressed through the micronization of the salts or minerals which are added to the liquid nutritional. Micronization is the comminuting of the salts and/or minerals to a particle size of about one .mu.m (10.sup.-6 meter or "micron") or less. It is believed that the reduced particle size of the salts and/or minerals will lessen their sedimentation. This approach is costly and any sedimentation which occurs is typically not able to be re-dispersed by shaking the container.
The use of a stabilizer such as carrageenan, carboxymethylcellulose and guar gums is well known in connection with solid food products. It must be appreciated that sedimentation and creaming are not nearly as much a problem in solid foods as they are in liquid nutritionals. In addition, the use of carrageenans and/or other hydrocolloids impacts the desired viscosity and flow characteristics of the liquid nutritional.
Viscosity of a liquid enteral nutritional under various levels of shear stress is a very important characteristic. High viscosity products (those over 0.05 Pa.cndot.s or 50 cps) 15 under high levels of shear stress, are not useful for tube feeding or through a nipple. As used herein and in the claims, the term "low viscosity" means a liquid nutritional product with a viscosity of less than about 0.05 Pa.cndot.s (50 cps) as measured by a Brookfield Viscometer using a #1 spindle at room temperature and at 60 rpm. Also important is the aspect of "yield stress". Yield stress means that upon the application of shear (force measured in dynes/cm.sup.2), the product will flow in a manner that is acceptable for tube or nipple feeding. An aspect of the present invention is directed to the discovery that 10 to 500 ppm of gellan gum provides reduced sedimentation while maintaining actual yield stress values in the range of 0.1 to 1.0 dynes/cm.sup.2. The term "actual yield stress" means values that are measured directly and not derived from a mathematical model.
U.S. Pat. No. 5,416,077 to Hwang et al. discloses a liquid nutritional composition containing from 50 to 1,000 parts per million of iota-carrageenan and optionally, kappa-carrageenan. This patent fails to disclose or suggest the use of gellan gums and the unexpected results that can be realized through the use of gellan gum in nutritionally complete liquid foods.
WO 94/24887 to Clark discloses a beverage stabilizing system which is a blend of gellan gum and carboxymethylcellulose. This application discloses that the gellan gum/carboxymethylcellulose system provides a weak, stabilizing gel structure suitable for beverage products. This application, which discloses stabilized chocolate milks and fruit juices, requires the combined use of gellan gum and a carboxymethylcellulose (CMC). Further it is stated that gellan gum alone does not provide enough structure to prevent settling. The beverage stabilizing blend of CMC and gellan gum, is disclosed as being in a weight ratio of between about 3:1 to 20:1.
European Patent Application 045437382 to Colegrove discloses the use of gellan gum fibers, produced by extrusion into a gelling salt bath, as wound dressings and catamenial devices. It is further disclosed that other gums may be coextruded with the gellan gum to produce useful fibers.
U.S. Pat. Nos. 5,190,778 and 5,196,220 to Clare et al. discloses fermented malt beverages (beers) having improved foam stability and desirable lace, cling and clarity. It is disclosed that the beverage is stabilized by adding 5 to 400 ppm by weight of gellan gum. These patents do not suggest or disclose the use of gellan gums to overcome the problems associated with the sedimentation of calcium, phosphorous, insoluble fibers and flavoring powders, such as cocoa, in nutritionally complete liquid formulas.
An article entitled "Mechanical Properties of Gellan Gels in Relation to Divalent Cations" by Tang et al. Journal of Food Science, Vol. 60, No. 4, (1995) discusses the mechanical properties of gellan gels containing different polymer and cation concentrations. The article states that at a given concentration of gellan gum, the gels were extensible below the critical cation level and brittle above that level. This reference fails to suggest or disclose a solution to the unique problems associated with stabilizing nutritionally complete liquid formulas or that such formulas would benefit from the inclusion of from 10 to 500 parts per million (ppm) of gellan gum.
Hannigan in Food-Engineering, 55(1), pages 52-53 discusses gellan gum which is produced by controlled fermentation of Pseudomonas elodea and deacetylation. Gellan gum is disclosed as requiring a cation, preferably calcium, for gelation. Gellan gum is suggested as a replacement for several different commercially used gelling agents utilized in the manufacture of foods. Recited applications include jellies, deserts, retorted and ultra high temperature (UHT) processed solid foods, beverages and milk products (ice cream, cheese, yogurt and the like).
Gellan gums are sold by the Kelco Division of Merck & Co. under the KelcoGel.RTM. brand name. Gellan gums are known as multi-functional gelling agents for use in foods, pet foods, personal care products and industrial applications. Gellan gums have been approved by the U.S. Food & Drug Administration for use in foods and have been developed specifically for bakery fillings, confections, icings, frostings, glazes, jams, jellies, puddings and personal care products.
Gellan gum is a high molecular weight extracellular heteropolysaccharide produced by fermentation of a culture of Pseudomonas elodea, ATCC 31461. During fermentation, oxygen, temperature and pH are strictly controlled. When the fermentation is complete, the gellan gum is isolated from the broth by alcohol extraction and dried. It is known that gellan gums form gels with a wide variety of cations, notably calcium (Ca 2+), magnesium (Mg 2+), sodium (Na+), potassium (K+) and also hydrogen ions (H+) from acid. These cations cause the gellan molecules to associate and form a gel. Calcium and magnesium are known to be much more efficient gel formers than sodium or potassium.
Historically, carrageenans have been used to suspend calcium and phosphorous and reduce sedimentation and the compaction of the sediment. Products containing high levels of calcium, phosphorous, dietary fiber and other insoluble agents, such as cocoa powder, are especially susceptible to sedimentation, and the conventional stabilizing systems leave much to be desired. Further, the use of carrageenans has been identified as a bowel irritant to people consuming products that contain high levels of this stabilizer and certain countries around the world do not permit the use of carrageenans in food products.
Thus, a need exists to improve the physical stability of nutritionally complete, low viscosity formulas while reducing or eliminating the use of carrageenans. While the liquid nutritionals of this invention are particularly suited for infant formulas and medical nutritionals, it is contemplated herein that the invention would also be useful for any liquid nutritional that has encountered the problems of sedimentation.